> Simon, > > Leave the TDS1 meter alone it is not an instrument to meassure ppm. > The name implies Totally Dissolved Solids and CS IS NOT a totally > disolved solid.
I want to provide a *little* bit of balance to Bob Berger's comments. The Hanna TDS-1 meter is a *conductivity* meter that features temperature compensation and readout in equivalent ppm of (I believe) a standardized calcium chloride solution. It will give you a reading that is ENTIRELY a function of conductivity. That is *ALL* that it does. In fact, the better instrument of this kind for our purpose would be the Hanna PWT (Pure Water Tester) which is essentially the same instrument as the TDS-1, with more sensitive electronics that are better matched to the conductivity range of our usual samples. It reads out in microSiemens which is a unit of conductivity. So the PWT provides a more direct and honest result than "equivalent ppm of a standard solution of some particular salt." It would be a lot harder to decieve yourself into believing that you're somehow directly measuring true ppm. TO THE EXTENT that conductivity can be *related* to the actual concentration of silver in a particular sample of CS, both of these Hanna devices will give a good, stable, and repeatable measurement. We do not know *HOW* conductivity is related to concentration across the many possible variables of CS production. But, it is my contention that you can evolve a calibration curve specific to a particular, very narrowly defined set of conditions. It will only be accurate if you keep your setup and procedures consistent and stay within the range of concentrations you have VERIFIED BY OTHER METHODS. BOB B.: Do you agree with what I've written so far? If not, it would be very good to know what you disagree with and why. I use my TDS-1 to test the quality of my distilled water. I also use it as a simple cross check against my current readings to decide when to stop a run. I *know* that all I'm seeing at this point is that my CS has the same conductivity as an X ppm solution of a given salt. But I *also* know that the reading relates well to the concentration of silver I got on my *last* batch, *and* on the batches made with that same recipe on the same equipment that I had tested by Bob, or my local environmental lab, or any other sources of proper analysis services. > I suspect you are new on the list. The peole to ask are Ivan, James > Holeman, brooks bradley, or myself. Bob, you and the others you listed are among the technical elite of this list, I agree. I don't think you really want to exclude all the rest of us from consideration, though. There is always room for debate, here or there, isn't there? I hope? Also, I would never blame the newcomers for what they don't already know when the information is just not available elsewhere! They're not stupid, or they wouldn't be asking questions! > When I first got on this list the TDS was a great item, but I have a > spectrophotometer for measuring ppm. So I bought one to debunk the > whole mess. IT DOES NOT WORK. It works very well doing the job it was designed for, which is interpreting *CONDUCTIVITY* into some standard unit of measure. Correlated with Bob's spectrometer readings or the other standard measurement techniques, it *can* give an approximate measurement of "ppm" over a very narrow range of conditions and concentrations. By itself it can be *useful* to assure repeatability between batches and even stability in storage. You just cannot really say what "ppm" you have unless you've done the additional work of getting your CS tested by other means. I'm not trying to encourage or discourage anyone from buying one of these devices. I just want everyone to understand what they *are* good for. Be well, Mike D. [Mike Devour, Citizen, Patriot, Libertarian] [mdev...@mail.id.net ] [Speaking only for myself... ] -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: silver-list-requ...@eskimo.com -or- silver-digest-requ...@eskimo.com with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: silver-list@eskimo.com List maintainer: Mike Devour <mdev...@id.net>
